1. Field of the Invention
The present invention relates to a cathode-ray tube for color picture tube color monitor and the like, and more particularly, to a cathode-ray tube having a yoke mounting part of a funnel in a pyramidal form for mounting a deflection yoke so as to both secure the margin of beam strike neck (BSN) according to wide-angle deflection and enhance atmospheric pressure resistance.
2. Background of the Related Art
In general, a color cathode-ray tube, for example, has an outer vacuum tube that comprises a glass face panel having an approximately rectangular display space, a glass funnel joined to the face panel, and a cylindrical glass neck joined to the funnel.
The neck is internally provided with electron guns emitting three electron beams, and a deflection yoke is provided around the circumference of the neck and the funnel.
The funnel has a yoke mounting part extending from the joint with the neck to the mount position of the deflection yoke.
An in-line type self-converging color cathode-ray tube is widely used that uses non-uniform magnetic fields in converging three in-line type electron beams over the whole screen without a separate compensator by deflecting three electron beams, emitted from electron guns in a line on the same horizontal plane, with a pincushion-shaped horizontal deflection magnetic field and a barrel-shaped vertical deflection magnetic field generated from the deflection yoke.
Such a general cathode-ray tube has the deflection yoke usually designed based on the funnel. However, in a pyramidal funnel and deflection yoke structure, the cone of the funnel, i.e., the yoke mounting part has to be designed to have an optimal inside profile as determined in consideration of the explosion characteristic and the BSN to the beam trajectory, the funnel being designed based on the deflection yoke in the order of deflection yoke design, deflection yoke profile modeling, magnetic field calculation, beam trajectory calculation, vacuum stress calculation at the funnel bulb, and deflection yoke shape modeling considering deflection sensitivity. This constraint on designing the yoke mounting part requires optimization in designing the outside profile of the funnel so as to enhance atmospheric pressure resistance in consideration of deflection sensitivity and explosion characteristic in a situation that the values related to the inside profile of the funnel are almost fixed.
A color cathode-ray tube is illustrated in FIGS. 1 and 2 as an example of the above-constructed conventional cathode-ray tube.
The color cathode-ray tube has an outer vacuum tube 10 made of glass.
The outer vacuum tube 10 comprises a face panel 3 having an approximately rectangular effective part 1 and a skirt part 2 provided in the periphery of the effective part 1, a funnel 4 joined to the skirt part 2, and a cylindrical neck 7 extending from the funnel 4.
The effective part 1 of the face panel 3 has an approximately rectangular form with horizontal and vertical axes H and V perpendicular to each other through a tubular axis Z of the cathode-ray tube.
And, a deflection yoke 6 is externally provided over an area ranging from the neck 7 to the funnel 4. The funnel 4 has a small-diameter region, so-called yoke mounting part 12 extending from the joint with the neck 7 to the mount position of the deflection yoke 6, i.e., extending to the side of the face panel 3.
On the inner surface of the effective part 1 of the face panel 3 are provided a fluorescent screen 5 comprising three dot or stripe type fluorescent layers emitting blue, green and red lights, and a stripe type light-shielding layer interposed between the fluorescent layers.
The outer vacuum tube 10 is internally provided with a shadow mask 11 as a dichroic electrode opposite to the fluorescent screen 5.
And, electron guns 9 emitting three electron beams 8 are provided in the neck 7. The three electron beams 8 emitted from the electron guns 9 are deflected by the horizontal and vertical magnetic fields generated from the deflection yoke 6, thus horizontally and vertically scanning the fluorescent screen 5 via the shadow mask 11 to form a color image on the screen 5.
The yoke mounting part 12 of the funnel 4 in which the deflection yoke 6 is mounted in the color cathode-ray tube has an approximately pyramidal form. Here, the deflection yoke 6 is of a saddle shape with less leakage magnetic field and comprises a cylindrical frame made of a synthetic resin for fixing horizontal and vertical deflecting coils and a core. More specially, the pyramidal yoke mounting part 12 has a circular cross section perpendicular to the tubular axis Z as the neck 7 around the joint with the neck 7 and an approximately rectangular cross section in conformity with the profile of the effective part 1 of the face panel 3, as shown in FIGS. 3 and 4, around the central portion along the tubular axis Z and the end portion on the side of the fluorescent screen 5.
As illustrated in FIG. 4, the cross section of the yoke mounting part 12 has the outside profile in an approximately rectangular form constituted by the continuity of a pair of circular arcs 20 for a horizontal radius Roh having a center on the horizontal axis H with respect to the effective part 1, a pair of circular arcs 21 for a vertical radius Rov having a center on the vertical axis V, and a pair of circular arcs 22 for a diagonal radius Rod having a center on the diagonal axis D.
That is, as shown in FIG. 3, the cross section of the yoke mounting part 12 has the inside profile with inner diameters La, Sa and da in the directions of horizontal (major), vertical (minor) and diagonal axes H, V and D, respectively, extending from the joint with the neck 7 to the end of the deflection yoke 6.
The yoke mounting part has, as also shown in FIG. 3, outer diameters DA, LA and SA in the directions of diagonal, horizontal (major) and vertical (minor) axes D, H and V, respectively, extending from the joint with the neck 7 to the screen side of the deflection yoke 6, i.e., the end of the deflection yoke 6.
As such, the cross section of the yoke mounting part 12 perpendicular to the tubular axis Z has the outside profile almost in the same circular form as the neck 7 around the joint with the neck 7, and in an approximately rectangular form on the side of the fluorescent screen 5 with a gradual decrease in the outer diameters LA and SA in the directions of the major and minor axes, respectively, with respect to the outer diameter DA in the direction of the diagonal axis D.
While on the other, the yoke mounting part 12 has the inside profile not in a perfect plane but in a pincushion form protruding in the direction of the tubular axis Z, as illustrated in FIG. 3. That is, the cross section perpendicular to the tubular axis Z of the yoke mounting part 12 has the inside profile not in a perfect rectangular form but in an imperfect rectangular form of which the sides form a convex curve protruding in the direction of the tubular axis Z.
Each short side 24 for the inside profile of the yoke mounting part 12 is in the form of a convex curve having an apical part on the horizontal axis H, each long side 25 being in the form of a convex curve having an apical part on the vertical axis V.
In a case where the long and short sides 25 and 24 for the inside profile are in the form of a convex curve, the individual corners are all formed with arc curves, i.e., arcs 22 and 26 in both inside and outside profiles so as to prevent an abrupt decrease in the thickness in the vicinity of the corners that may be caused by a difference between inner and outer diameters La and LA in the direction of the horizontal (major) axis, and a difference between inner and outer diameters Sa and SA in the direction of the minor axis.
The long and short sides perpendicular to the tubular axis Z with respect to the inside profile of the yoke mounting part 12 have such a thickness as determined based on the profile of an electron beam passage region 23 in the yoke mounting part 12.
Therefore, as described above, the cross section of the yoke mounting part 12 has an inside profile formed with convex curves in the form of a pincushion approximate to the electron beam passage region 23, thereby converging the inside of the yoke mounting part 12 on the electron beam passage region 23. For example, a gap between the inside of the yoke mounting part 12 and the electron beam passage region 23 is approximately 1 mm.
The cross section of the yoke mounting part 12 of the funnel 4 has the outside profile in an approximately rectangular form, with the inside profile having the respective sides in the form of a convex curve protruding in the direction of the tubular axis Z. This approximates the inside of the yoke mounting part 12 to the electron beam passage region 23 and enhances deflection efficiency of the deflection yoke 6 to reduce deflection power consumption.
Such a pyramidal yoke mounting part 12 enables reduction of the horizontal and vertical diameters in the directions of the horizontal (major) and vertical (minor) axes H and V of the deflection yoke 6, respectively. Thus the horizontal and vertical deflecting coils of the deflection yoke 6 become closer to the electron beams 8 to efficiently deflect the electron beams 8 and reduce deflection power consumption.
The above-stated cathode-ray tube may reduce deflection power consumption simply by decreasing the diameter of the neck 7 or the outer diameters of the yoke mounting part 12 of the funnel 4. But, as the cross section of such a yoke mounting part 12 approximates a rectangular form, deformation occurs in originally flat vicinities 100 and 101 of the horizontal and vertical axes H and V in the directions as indicated by broken lines 103 of FIG. 5 due to a load F of the atmospheric pressure. The deformation causes compressive stresses sH and sV on the outer surface of the vicinities 100 and 101 of the horizontal and vertical axes H and V of the yoke mounting part 12 and an excessive tensile stress sD on the outer surface of a vicinity 102 of the diagonal axis D, as a result of which the outer vacuum tube 10 has a deterioration of the atmospheric pressure resistance and safety.
In the aspect of this problem, Japanese Patent Pyung10-154472 discloses a yoke mounting part of the funnel 4 in the form of a pyramid that reduces the distance from the deflection yoke to the electron beams in order to prevent occurrence of a neck shadow and deterioration of atmospheric pressure resistance.
The cross section of such a yoke mounting part has inside and outside profiles with two horizontal sides opposite to each other based on the horizontal axis interposed between them in the form of a straight line and two vertical sides opposite to each other based on the vertical axis between them in the form of a convex curve protruding in the direction of the tubular axis, so that the atmospheric pressure resistance and the margin of BSN are secured due to the difference in the thickness between the long or short sides and the corners.
However, with an excessive difference in the thickness between the long or short sides and the corners in order to secure the margin of BSN, the pyramidal cathode-ray tube according to Japanese Patent Pyung10-154472 may have an increase in the maximum vacuum strength (tensile strength) on the corners of the funnel to cause explosion of an exhaust gas in the manufacture of the cathode-ray tube and increment the distance from the deflecting coils to the electron beam passage region, thus increasing deflection power consumption. Otherwise, when the thickness difference between the long or short sides and the corners is decreased in order to prevent explosion and reduce deflection power consumption, an excessive stress occurs on the BSN and the long and short sides.
Especially, in a case of wide-angle deflection with the pyramidal funnel yoke structure, the inside profile has the form of a pincushion and the outside profile has the form of a straight line so that long sides are more deteriorated in strength than short sides.
It is, therefore, an object of the present invention to provide a cathode-ray tube that minimizes the atmospheric pressure stress imposed on the funnel, in which a yoke mounting part has inside and outside profiles uniform in thickness along the horizontal (major) and vertical (minor) axes according to the deflection angle of electron beams with respect to a diagonal axis of the yoke mounting part, with the long and short sides having a different thickness from each other, thereby enhancing the strength of a weak portion.
It is another object of the present invention to provide a cathode-ray tube that secures the margin of neck shadow and the atmospheric pressure resistance of the funnel, in which a yoke mounting part has inside and outside profiles uniform in radius along the horizontal (major) and vertical (minor) axis according to the deflection angle of electron beams with respect to a diagonal axis of the yoke mounting part, thus optimizing the thickness ratio according to the position based on the length of each axis.
It is further another object of the present invention to provide a cathode-ray tube that minimizes the atmospheric pressure stress imposed on the funnel and enhance deflection sensitivity, in which a yoke mounting part divided into equal xe2x80x9cnxe2x80x9d parts has an optimized ratio of the diagonal thickness to the horizontal or vertical thickness perpendicular to the tubular axis per a regular interval at each position.
It is still further another object of the present invention to provide a cathode-ray tube that secures the margin of neck shadow and minimizes deflection power consumption, in which a yoke mounting part has a ratio of the diagonal radius of inner curvature to the diagonal radius of outer curvature in an appropriate range, thus approaching the magnetic fields of the deflecting coils to the electron beams based on the deflection angle of the electron beams as much as possible.
To achieve the above objects of the present invention, in a cathode-ray tube which has a panel provided with a fluorescent screen on an inner surface thereof, a funnel joined to the panel, a neck joined to the funnel and provided with electron guns facing the fluorescent screen, and a pyramidal yoke mounting part provided in a region extending from the neck side to the panel side, the yoke mounting part is defined to extend from a joint with the neck to at least the end of a deflection yoke on the side of the screen and includes: an inside profile having a form protruding towards a tubular axis in the direction of major and minor axes based on a diagonal axis so as to have a functional relation with a deflection angle; and an outside profile having an approximately rectangular form with respect to the major and minor axes. The outside profile has a ratio of maximum thicknesses in the direction of the minor and major axes in the range from 1.0 to 1.2.
In another aspect of the present invention, there is provided a cathode-ray tube which has a panel provided with a fluorescent screen on an inner surface thereof, a funnel joined to the panel, a neck joined to the funnel and provided with electron guns facing the fluorescent screen, and a pyramidal yoke mounting part provided in a region extending from the neck side to the panel side, the yoke mounting part being defined to extend from a joint with the neck to at least the end of a deflection yoke on the side of the screen, the yoke mounting part including: an inside profile having a form protruding towards a tubular axis in the direction of major and minor axes based on a diagonal axis so as to have a functional relation with a deflection angle; and an outside profile having a rectangular form with respect to the major and minor axes, the outside profile having a ratio of a maximum thickness to a minimum thickness on the same axis being either of the minor or major axis in the range from 1.0 to 1.5.
In further another aspect of the present invention, there is provided a cathode-ray tube which has a panel provided with a fluorescent screen on an inner surface thereof, a funnel joined to the panel, a neck joined to the funnel and provided with electron guns facing the fluorescent screen, and a pyramidal yoke mounting part provided in a region extending from the neck side to the panel side, the yoke mounting part being defined to extend from a joint with the neck to at least the end of a deflection yoke on the side of the screen; and when a tubular axis ranging from the joint with the neck to the end of the deflection yoke is divided into equal xe2x80x9cnxe2x80x9d parts, a value of Td/Tv or Td/Th being in the range from 0.5 to 0.85, wherein Tv, Th and Td are thicknesses in the directions of minor, major and the diagonal axes, respectively, perpendicular to the tubular axis at each length-based position.
In still further another aspect of the present invention, there is provided a cathode-ray tube, which has a panel provided with a fluorescent screen on an inner surface thereof, a funnel joined to the panel, a neck joined to the funnel and provided with electron guns facing the fluorescent screen, and a pyramidal yoke mounting part provided in a region extending from the neck side to the panel side, the yoke mounting part being defined to extend from a joint with the neck to at least the end of a deflection yoke on the side of the screen. When a tubular axis ranging from the joint with the neck to the end of the deflection yoke is divided into equal xe2x80x9cnxe2x80x9d parts, it satisfies 0.5xe2x89xa6Td/Tvxe2x89xa60.85 and 0.5xe2x89xa6Td/Thxe2x89xa60.85, wherein Tv, Th and Td are thicknesses in the directions of minor, major and the diagonal axes, respectively, perpendicular to the tubular axis at each length-based position; and 0.35xe2x89xa6Rid/Rodxe2x89xa60.67, wherein Riv and Rov are radii of inner and outer curvatures in the direction of the minor axis perpendicular to the tubular axis, respectively; Rih and Roh are radii of inner and outer curvatures in the direction of the major axis perpendicular to the tubular axis, respectively; Rid is a radius of inner curvature at a corner approximating Riv and Rih; and Rod is a radius of outer curvature at the corner approximating Rov and Roh.